Hematologic and Renal Trends in Cats Undergoing Continuous Renal Replacement Therapy: A Retrospective Case Series with Molidustat Use

Continuous renal replacement therapy (CRRT) can precipitate anemia in critically ill patients, but temporal hematologic trends and anemia management strategies in cats remain poorly characterized. Medical records of three client-owned cats treated with CRRT for severe acute kidney injury with evidence of pre-existing chronic kidney disease at a single referral center were retrospectively reviewed. Hematologic variables (hematocrit, hemoglobin concentration, absolute reticulocyte count) and renal parameters (blood urea nitrogen, creatinine, phosphorus) were evaluated before, during, and after CRRT, along with the timing of CRRT sessions, whole blood transfusions, erythropoiesis-stimulating agent administration, and adjunctive molidustat use. All three cats demonstrated a progressive decline in hematocrit during the CRRT period despite repeated whole blood transfusions, with only transient post-transfusion improvement. Blood urea nitrogen and creatinine concentrations decreased promptly following CRRT initiation but showed variable rebound patterns during follow-up. Absolute reticulocyte counts increased after CRRT discontinuation in two cats, indicating preserved or recovering erythropoietic activity, while one cat with concurrent inflammatory and infectious disease showed a minimal response. Progressive anemia occurred consistently despite transfusion support, highlighting the multifactorial nature of anemia during feline CRRT. These descriptive findings provide clinically relevant insight into anemia progression during feline CRRT and may inform the design of future prospective studies.